Recoverable article

ABSTRACT

A recoverable article comprising an inner resilient tubular member that is held out in a laterally expanded configuration by engagement with outer holdout structure, wherein the outer surface of the inner member is provided with a plurality of cavities, and wherein the holdout structure occupies the cavities so as to provide the holdout engagement, wherein the holdout structure comprises at least one initiating portion that is structurally different from the remaining portion that engages at least one associated cavity, whereby release of the initiating portion from its cavity facilitates subsequent release of the remaining portion of the holdout structure.

This invention relates to a recoverable article for, and method of,enclosing an elongate substrate. The substrate may comprise for examplea cable, which may be an electrical power or telecommunications cable,and in particular a cable connection. The cable connection may comprisea joint, or splice, between two, or more, cables, or a termination of acable, for example on to a terminating lug or bushing connected toelectrical equipment such as switchgear or a transformer. Thetermination may comprise an adapter, for example an elbow.

The invention will be further particularly described with reference toan in-line joint between two electric power cables, but it is to beunderstood that this is by way of example only and not by way oflimitation.

Joints between two power cables, whether either or both are polymeric orpaper insulated cables, need to be enclosed within a protectivearrangement that includes an electrically insulating layer. Heat shrinktechnology has been applied for this purpose for many years, withproducts available from Raychem and others. However, technologies thatdo not require heat are also employed. Push-on sleeves and elbows areavailable but unlike heat shrinkable products, these have severerange-taking limitations that necessitate a large inventory. Otherso-called cold applied solutions require a tubular elastomeric sleeve tobe radially expanded and mounted on a rigid holdout member, the internaldiameter of which is larger than the maximum outer diameter of the cablejoint to be enclosed. One example of the latter is the PST sleeveavailable from 3M, as exemplified in U.S. Pat. No. 3,515,798. Such asleeve has an inner holdout member that consists of a continuous narrowstrip of tough flexible material in the form of a rigid closed helixhaving adjacent coils interconnected. The held out sleeve is mountedover the cable joint and the helical strip is then unwound, thusallowing the insulating stretched elastic cover to shrink down onto thejoint. However, it is inconvenient having to unwind the holdout striphelically around the extended cable, especially if the work has to bedone in the confined space of a trench or manhole. Another example of acold applied arrangement is disclosed in U.S. Pat. No. 3,824,331 (AMP),in which a resilient tubular cover is supported in a stretched conditionby an easily removable external one piece support member, each end ofthe cover being rolled back over the outside of the support. The coverand support member are mounted on an internal sleeve in the form of alongitudinally slit tube held in a state of increased diameter by adividing strip in the shape of an I-beam. When in position over thecable joint, removal of the dividing strip longitudinally from the slitallows the inner tube to be squeezed and then freely withdrawn from thecover. The cover ends are then unrolled onto the adjacent cable sectionsand the external support member is removed. It will be appreciated thatsuch an arrangement requires an inner and an outer holdout member, eachof which has to be removed. EP-B-0 530 952 (3M) discloses a coverassembly in which an elastomeric tube is held out in a stretchedcondition on an inner support core. The core is frangible such thatapplication thereto of a force beyond that produced by the tube causesbreakage of the core so as to allow contraction of the elastomeric tubeonto the substrate. The fragments of the collapsed core remain withinthe tube and must therefore be as small as possible to facilitateaccommodation therewithin.

With each of these arrangements, the holdout member is disposedinternally of the sleeve that is to be applied to the substrate cable.Thus, the sleeve cannot conveniently have an internal coating, of gel,mastic or adhesive for example, applied thereto. This problem, isavoided by the recoverable sleeve assembly disclosed in U.S. Pat. No.4,410,009 (Sigmaform), in which an inner elastomeric tube is maintainedin a radially-stretched condition by having an outer rigid tubesurrounding and secured to the outer surface thereof. The outer tube isa rigid thermosetting adhesive polyurethane whereby the outer tube issufficiently adhesive to hold the inner tube in its stretched conditionbut will peel from the inner tube upon impact of force. U.S. Pat. No.4,070,746 (Raychem) discloses a recoverable tubular article in which anelastomeric sleeve is retained in a radially expanded condition by anouter constraint that is bonded thereto. The restraint is sufficientlystrong to retain the sleeve in its expanded form under ordinaryconditions of storage, but is susceptible to attack by solvents thatweaken the bond sufficiently to allow the elastomeric sleeve to peelaway from the restraint and to recover towards its original state. U.S.Pat. No. 4,233,731 (Raychem) discloses a dimensionally-recoverablearticle comprising a hollow resilient member which has been expanded toa dimensionally unstable configuration in which it is retained by akeeper positioned between and separating two parts of the hollow memberaway from the path of recovery thereof. The keeper is made from amaterial that weakens or changes its shape upon heating and/or chemicaltreatment, for example by being chemically degradable when subjected toa solvent. In one embodiment a single wedge of fusible material isinterposed in the break in the circumference of a split tube ofberyllium copper alloy. In another embodiment a tubular member made froman engineering plastics material has dovetailed protuberances on itsouter surface between which strips of a polycarbonate are inserted tomaintain the expanded configuration. EP-A0590469 (Kabelmetal) disclosesa recoverable elastomeric tubular article that is held in its expandedstate by thermoplastic bracing means in the form of a profile appliedhelically to the outer surface of the expanded tube.

It is an object of the present invention to provide a recoverablearticle and its method of manufacture, in which the article is held outin its expanded configuration by an advantageous external holdout meansso as not to interfere with any inner layer, of gel, adhesive or masticmaterial for example, which may be applied internally thereof as acoating or which may be located around the substrate to be enclosed.

Thus, in accordance with one aspect of the present invention, there isprovided a recoverable article comprising an inner resilient tubularmember that is held out in a laterally expanded configuration byengagement with outer holdout means, wherein the outer surface of theinner member is provided with a plurality of cavities, and wherein theholdout means occupies the cavities so as to provide the holdoutengagement, wherein the holdout means comprises at least one initiatingportion that is structurally different from the remaining portion thatengages at least one associated cavity, whereby release of theinitiating portion from its cavity facilitates subsequent release of theremaining portion of the holdout means.

The forces generated within an expanded resilient member tending tocause it to recover can be large, the more so the thicker is the wall ofthe material. Thus, although such a cavitied member can be expanded andkept in its expanded configuration by maintaining the enlarged size ofthe cavities, in some instances it can be found to be extremelydifficult, due to high frictional forces, to remove the holdout means inorder to allow the member to recover towards, or, in the absence of anunderlying substrate, to its original configuration. This difficulty isexacerbated the larger is the interface between the holdout means andthe member, such as for example where the holdout means comprises astrip filling a cavity in the form of a long channel. It can be almostimpossible to remove such a strip from the channel. By providing theholdout means with an initiating, or trigger, portion that isstructurally different from the remaining portion, the initiatingportion can be arranged to be released more easily, and advantageouslymanually, thereby reducing the frictional forces retaining the remainingportion of the holdout in place, which can then itself also be removedmanually.

Preferably, the or each initiating portion comprises two parts such that(a) when the two parts engage one another, the integrity of the holdoutmeans is maintained, and (b) when one of the two parts is released fromthe other part that is in engagement with the cavity, the other part isremovable from the inner member. In such an article, release of the twoparts from each other may allow the other part to be ejected from thecavity by the recovery force of the resilient member.

In one embodiment, the trigger, or other, holdout means may comprise atleast one high modulus material strip engaging respective channels ofthe castellated outer surface of the inner member, each strip beingencased within a lower modulus sheath that retains a lubricant. Releaseof the holdout may be effected by slitting the outer sheath from one endto the other so that the lubricant facilitates the recovery force of theinner member urging the strips out of the channels. The slitting may beeffected by an annular ring with inwardlyprojecting cutting surfaces forengaging more than one holdout strip.

Advantageously, the release of the one part of the initiating portionmay result in the other part undergoing a change of shape, for exampleby a pivoting or hinging movement, that facilitates its removal from thecavity.

The two parts may interlock, be hinged together, and may be integrallyformed. Fracture of, for example cutting through, one of the parts mayallow a change of shape so that the other part can be removed from thecavity. Alternatively, one part may be inserted within the other therebyto maintain the shape of the other part to prevent collapse, orrecovery, of the cavity. In the latter embodiment, removal of the insertmay result in the recovery force of the member collapsing and ejectingthe other part.

The holdout means may comprise a plurality of initiating portionslocated symmetrically on the outer surface of the resilient member,whereby the remaining portion of the holdout means is relatively easilyremovable subsequent to removal of all the initiating portions. However,it is presently more preferred for there to be a single initiatingportion.

Advantageously, the cavities comprise a plurality of channels thatextend longitudinally of the article, preferably parallel to oneanother, and preferably parallel to the longitudinal axis of the tubularmember. Alternatively, the channels may extend helically wound aroundand along the resilient member. The channels may be of substantiallyrectangular configuration, but they may be re-entrant so as to enhanceretention of the holdout means therein. Preferably, the channels areprovided by the resilient member having a castellated outer surface.

The or each initiating portion and/or the remaining portion of theholdout means may comprise a plurality of strips that are retainedwithin respective ones of the channels. The strips are preferablyremovable by a peeling action from one end thereof to the other.

In a particularly preferred embodiment the initiating portion comprisesa single strip (which may comprise two or more parts), and the remainingportion of the holdout means comprises a plurality of other strips.Recovery of the resilient tubular member is carried out by removal ofthe initiating strip and subsequent removal of the other strips,preferably sequentially around the circumference of the tubular member.This method of recovery (shrinkage) of the tubular member has theadvantage that it helps to prevent entrapment of air beneath the memberwhen recovered.

In embodiments in which the holdout means comprises a plurality ofstrips, the article may include one or more (preferably two) supports,for example in the form of rings, to retain the tubular member(preferably via the holdout strips) , in a substantially circularcross-sectional configuration. The or each support is preferably locatedradially inwards of the holdout strips and/or the tubular member. The oreach support may be located adjacent to an end of the tubular member,preferably exterior to the tubular member.

One portion of the holdout means may be applied in a flowable form, suchas sand or other granular material, and held in place by a wrapping ofpolymeric or other suitable material. The flowable material may be ahardenable, or curable, material, such as plaster of paris, cement, acurable epoxy resin system or other thermoset, which may or may notrequire a wrapping.

In general, however, whether or not the holdout means is flowable, itmay be desirable to enclose the article of the invention within an outersheath to enhance retention of the holdout means during storage andtransport.

One portion of the holdout means may comprise foam, preferably highdensity foam, which may be formed in strips to fit channels in the outersurface of the inner member for example, or which may be foamed in situto fill the expanded cavities.

In a further embodiment the holdout may be formed by a layer extendingaround the entire circumference of the inner member and bonded theretoso as to extend over the top of the cavities. In its holdoutconfiguration, the layer may be deflected into the cavities, and may beflipped outwards, for example progressively from one end of the articleto the other, so as to hinge to a configuration that allows recovery ofthe article.

One portion of the holdout means may be formed, especially when of stripconfiguration, of material that exhibits good resistance to compressionin the transverse direction, whilst exhibiting more flexibility, orbrittleness, in the longitudinal direction of the inner member, therebyto facilitate controlled removal thereof, and thus controlled recoveryof the inner member. Cardboard has been found to be a suitable material,for example a material comprising composite layers of Kraft boardapproximately 0.9 mm thick. Wooden laths, fibre board or plasterboardare also suitable materials. In the latter case, a board comprising alayer of plaster 9 mm thick laminated between layers of cardboard givingan overall thickness of about 10 mm has been found suitable. Suchholdout means are comparatively cheap and are also bio-degradable. It isalso envisaged, however, that the holdout means of the article of theinvention may be polymeric, preferably bio-degradable.

The holdout means may be extruded on to the outer surface of the innertubular member.

Advantageously, the cavities, for example the longitudinal channels, inthe outer surface of the inner member are re-entrant so as to enhanceretention of the holdout means.

It will be appreciated that the shaping of the cavities has to be suchas to ensure that the inner member is retained in its expandedconfiguration under expected conditions of storage and transport to itsplace of application and then to be released without the need for undueforce, preferably manually, when the article is to be applied to asubstrate. The shaping of the interface between the inner member and theholdout means will thus depend on factors such as (i) the material ofthe inner tubular member and of the holdout means, in particular therelative hardness, and (ii) the force within the expanded tubular membertending to cause it to recover, which will itself depend on thematerial, the expansion ratio of the member, and its thickness. Thus,for example a thickwalled inner member made of highly expanded,relatively high modulus material would require a relatively greateramount of mechanical interlocking by the holdout means due to itsrelatively high recovery forces.

The inner member is preferably made from polymeric, preferablyelastomeric material.

One or both ends of the inner tubular member may advantageously have abevelled (especially chamfered) internal surface. This can help toprevent the end of the tubular member digging into a substrate (e.g. acable) around which it is recovered.

The inner member may form part of an enclosure for an electric cablesplice, termination, or the like, and may be formed from electricallyconductive material, for example for forming electrical continuityacross, and/or electrical screening of, the joint. The inner tubularmember may have one, or more, further layers on its inner surface, whichmay be co-extruded therewith. For example, an electrically insulatinglayer and/or an electrically stress grading polymeric layer may beco-extruded internally with the inner member. Such a layer may havedifferent mechanical properties from the inner member, for example bybeing more resilient so as to enhance conformity with the substrate, forexample a cable splice. There may also be an innermost electricallyconductive layer, for example extending along only part of the length ofthe other layer(s), to provide a Faraday cage. An inner layer of gel,mastic or adhesive may be provided to enhance conformability andsealing, for example to exclude air and/or moisture, with the substrate.It is also envisaged that such a sealant layer may be applied separatelyto the substrate.

In accordance with another aspect of the present invention, there isprovided a substrate, for example an electrical component, including anelectric cable splice, termination, or elbow, enclosed by a recoveredarticle in accordance with the said one aspect of the present invention.

In accordance with a further aspect of the present invention, there isprovided a method of recovering a recoverable e article in accordancewith the one a spect on to a substrate, by the steps of releasing the,or each, initiating portion of the holdout means from its cavity, andsubsequently releasing the remaining portion of the holdout means,preferably in a sequential manner around the circumference of thearticle. When in the form of strips, the holdout means is preferablyreleased by a peeling action from one end thereof to the other.Preferably there is a single initiating portion which is released,followed by the sequential release of the strips of the remainingportion of the holdout means.

Embodiments of recoverable article, their method of manufacture andapplication, each in accordance with the present invention, will now bedescribed, by way of example, with reference to the accompanyingdrawings, in which:

FIG. 1 is an end view of an article in its expanded configuration;

FIG. 2 is an isometric view of the article of FIG. 1 showing the firststep in its recovery;

FIG. 3 is an isometric view showing part of the length of the article ofFIG. 2 in its recovered form;

FIGS. 4 and 5 show partial end views of alternative recoverablearticles;

FIG. 6 shows a release member for use with the articles of FIGS. 4 and5; and

FIG. 7 is an isometric view of a recovered article forming part of anin-line power cable splice.

Referring to FIGS. 1, 2 and 3, the recoverable article comprises aninnermost elastomeric electrically insulating cylindrical tubular sleeve2, and, externally bonded thereto, an elastomeric electricallyconductive member 4 that has a castellated outer surface. An externalholdout arrangement consists of twelve relatively rigid polymeric stripsthat fill the twelve valleys of the castellated member 4 from one endthereof to the other. The holdout strips are of two kinds. The firstkind of holdout strip consists of four trigger strips 6 that areequispaced circumferentially around the tubular member 4, and these areinterspaced with the eight remaining strips 8 that are of a differentstructure.

Each strip 6 is in two parts, a generally H-shaped inner part IO thatengages the valley of the expanded tubular member 4, and a snap-on cover12. Each strip 8 consists of a hollow strip of rectangular section thatfits within its valley.

The composite recoverable member 2, 4, which may have been formed bymoulding or extrusion, is expanded such that the valleys on its externalsurface open up. The holdout strips 6, 8 are then pushed into positionand the expansion means, which may be an internal mandrel, is removed.The slight relaxation of the resilient recoverable member then firmlyretains the strips 6, 8 in position, and they, being relatively rigid,prevent further recovery of the article 2, 4. Removal of the strips 8 isparticularly difficult, if not impossible manually, due to the highfrictional forces that exist over the extensive surface area betweenthem and the castellation valleys or channels. The trigger strips 6,however, are designed structurally differently so as to be relativelyeasy to remove manually, and then, by releasing some of the recoveryforce on the strips 8, to facilitate manual removal of the remainingstrips 8.

The generally H-shape of the inner component 10 of the strips 6 allowsit to act as a hinge when the outer retaining cover 12 is removed. Thus,removal of the cover 12, as by the peeling action shown in FIG. 2,results in the circumferential recovery force within the resilientmember 4 exerting pressure on the radially inner legs of the H-shapedcomponent 10 which then hinges about its cross-member so that thecomponent 10 is urged out of its channel.

It is envisaged that the cover 12 would be removed completely,end-to-end, of each strip 6 in turn, resulting in ejection, or removal,of all four strips 6. This results in partial recovery of the compositearticle 2,4, and thus in an associated reduction in the stored recoveryforce. Consequently, the forces retaining the rigid tubular strips 8 inposition are reduced, so that the strips 8 can now be removed, therebyto allow full recovery of the article 2, 4. It will be appreciated thatunder free recovery, that is to say in the absence of a substrate, thearticle will tend to return to the size at which it was originallyformed. However, in practice, the article will be recovered on to asubstrate of such transverse dimension, usually diameter, that there isstill some unresolved recovery within the article thereby to enhance itsretention on, and sealing to, the substrate.

FIG. 3 shows an alternative mode of recovery of the article, in anintermediate stage. In this mode, the four trigger strips 6 areinitially released but only partway along the length of the article. Thestrips 8 are then released along the same length. This alternatingrelease of the two kinds of strips is then continued along the articleuntil it has recovered along its entire length.

FIG. 4 shows an end view of a segment of a further embodiment of therecoverable article in which a channel 80 between adjacent lands 82 ofthe outer surface of a resilient inner member is filled by a two-partelongate holdout strip 84. A central support part 86 of the strip 84 isof general-H shape with the narrow intermediate bridging portion forminga hinge. The other part of the holdout strip 84 consists of a pair ofside strips 88 that act to provide a lower friction interface with thecentral part 86 than the part 86 would have with the sides of the lands82.

Removal of the holdout 84 is achieved by means of the trigger ring 100of FIG. 6. The ring 100 is formed from a rigid plastics material and hasan annular portion 102 that is large enough to pass around the outsideof the article of FIG. 4, and a set of twelve tapering fingers 104 thatare axially directed and set on a circle of radius such that when thering 100 is positioned axially at one end of the article of FIG. 4, thefingers 104 engage with respective ones of the apertures formed betweenthe central support parts 86 and the bottom of the associated channels80. Thus, as the ring 102 is moved along the length of the recoverablearticle, the central support parts 86 are triggered so as to be pulledout of the channels, allowing the article to recover. The side strips 88may be removed separately, or may be left in place provided they do notinterfere with the recovery of the article and the subsequent reductionin the transverse dimension of the channels 80.

FIG. 5 shows a modification of the article of FIG. 4, in that thecentral support part 90 is of general hollow rectangular shape withexternal corners radiussed, and side strips 92 are wedge-shaped toconform to the correspondingly-shaped side walls of the channel of thecastellated inner member, and to enhance retention of the holdout part90 therein.

The trigger ring 100 of FIG. 6 will be arranged to engage the hollow ofthe central part 90, and the radiussing of its inner corners will assistin its ejection.

In a further embodiment, the reduction in friction achieved by employingside pieces of a holdout, such as the side strips 88 or 92, mayalternatively be achieved by spray coating the sides of the channels ofthe inner member or the holdout part 84, 90 with a low frictionmaterial, or by applying a grease thereto.

In the last mentioned embodiments of the invention, a retaining sheathmay be needed to retain the holdout strips in position until theirrelease is required. In such instances, the ring 100 of FIG. 6 may notbe required.

FIG. 7 shows an article 140, which may be in accordance with any one ofthe preceding embodiments, in its recovered condition on an in-lineelectric power cable splice. The article 140 consists of a castellatedelectrically conductive resilient member 142 and an innermost layer 144of polymeric electrically insulating material. Each cable has an outerpolymeric jacket 146, folded back earth screen wires 148, and primarydielectric 150. Prior to the recovery of the article 140, the regionaround the connector of the cable conductors (not shown) has beenenclosed within a layer 152 of stress controlling material, that hasbeen compressed into conformity with the underlying components by therecovery of the article 140, thereby excluding air from the spliceregion. Although not shown, it will be understood that an outerprotective jacket is to be applied to the splice as shown in FIG. 7 soas to encompass the article 140 and to seal on to each cable jacket 146.Electrical continuity across the joint, via the conductive layer 142,between the cable wires 148 will also be made. Advantageously, the outerprotection jacket is as disclosed in British Patent Application No.9626364.5, the entire contents of which are included herein by thisreference.

It will be appreciated that it may be advantageous to locate the triggerportion(s) of the holdout means of the invention symmetrically aroundthe inner tubular member, but this need not be the case. Furthermore,the number of trigger portions with respect to the number of remainingportions can be varied to suit the particular article. The recovery modemay be different from the examples given, with, for example, some of theremaining portion being removed before all the trigger portion has beenremoved. As a further alternative, the entire trigger portion, forexample all four trigger strips 6, may be removed substantiallysimultaneously, followed by substantially simultaneous removal of theremaining holdout portion, for example the strip 8. In the latterembodiment, a release means functionally corresponding to that shown inFIG. 6 may be devised to remove the covers 12 of the strips 6 and thento remove the strips 8.

What is claimed is:
 1. A recoverable article comprising an innerresilient tubular member that is held out in a laterally expandedconfiguration by engagement with outer holdout means, wherein an outersurface of the inner member is provided with a plurality of cavities,and wherein the holdout means occupies the cavities so as to provide theholdout engagement, wherein the holdout means comprises at least oneinitiating portion that is structurally different from a remainingportion that engages at least one associated cavity, whereby release ofthe initiating portion from its cavity facilitates subsequent release ofthe remaining portion of the holdout means.
 2. An article according toclaim 1, wherein the or each initiating portion comprises two parts suchthat (a) when the two parts engage one another, the integrity of theholdout means is maintained, and (b) when one of the two parts isreleased from the other part that is in engagement with the cavity, theother part is removable from the inner member.
 3. An arrangementaccording to claim 2, wherein release of one of the two parts of theinitiating member allows the other part to be ejected from the cavity bythe recovery force of the inner member.
 4. An article according to claim2, wherein said one part of the initiating portion comprises aninterlocking cover for the other part.
 5. An article according to claim2, wherein the two parts of the initiating portion are integral witheach other.
 6. An article according to claim 2, wherein the two partsare hinged together.
 7. An article according to claim 2, whereinfracture of the one part allows the removal of the other part.
 8. Anarticle according to claim 2, wherein said one part is inserted withinthe other part thereby to prevent change of shape thereof.
 9. An articleaccording to claim 2, wherein on the release of the one part of theinitiating portion, the other part undergoes a change of shape thatfacilitates its removal from the cavity.
 10. An article according toclaim 9, wherein the change of shape is effected by a pivoting movementof the other part of the initiating portion.
 11. An article according toclaim 1, wherein the remaining portion of the holdout means is retainedby the inner member until the at least one initiating portion has beenremoved therefrom.
 12. An article according to claim 1, wherein thecavities comprise a plurality of channels that extend longitudinally ofthe article, parallel to one another.
 13. An article according to claim12, further comprising one or more supports located radially inwards ofthe holdout strips to retain the tubular member in a substantiallycircular cross-sectional configuration.
 14. An article according toclaim 12, wherein the or each initiating portion and/or the remainingportion of the holdout means comprises a plurality of strips that areretained within respective ones of the channels.
 15. An articleaccording to claim 14, wherein at least the strips of the remainingportion of the holdout means are rigid relative to the material of theinner member.
 16. An article according to claim 14, wherein there is asingle initiating portion, comprising a single strip.
 17. An articleaccording to claim 14, wherein each strip comprises a plurality oflongitudinally spaced-apart holdout members that substantially fill acavity at discrete positions along its length, successive holdoutmembers of each strip being linked together.
 18. An article according toclaim 1, wherein the outer surface of the inner member is castellated.19. An article according to claim 1, wherein at least one portion of theholdout means comprises: (a) a particulate material; or (b) a curedmaterial; or (c) high density foam material; or (d) compacted fibrousmaterial; said material being retained in place by an enveloping cover,if required.
 20. An article according to claim 1, wherein the holdoutmeans comprises form-stable bio-degradable material.
 21. An articleaccording to claim 1, wherein the inner tubular member is electricallyconductive.
 22. An article according to claim 1, wherein the innertubular member is made from polymeric elastomeric material.
 23. Anarticle according to claim 1, comprising an additional, radially inner,resilient tubular arrangement on which the inner tubular member ismounted integrally therewith.
 24. An article according to claim 23,wherein the additional tubular arrangement comprises at least onetubular member that is more resilient than the inner resilient tubularmember.
 25. An article according to claim 23, wherein the additionaltubular arrangement comprises an electrically insulating tubular memberand/or an electrically stress-controlling tubular member.
 26. An articleaccording to claim 23, comprising an innermost electrically conductivelayer radially inwards of the additional tubular arrangement, andlocated only in a longitudinally central region of the article so as toprovide a Faraday cage.
 27. An article according to claim 23 wherein theadditional tubular arrangement is made from polymeric material.
 28. Anarticle according to claim 1, in which at least one end of the innertubular member has a bevelled internal surface.
 29. An article accordingto claim 1, of substantially right-cylindrical configuration.